Some of the worst invasive plants are actually quite lovely, as you will see by viewing the photos on the following pages. The old adage of not being able to judge a book by its cover very much pertains to such barbarians. In fact, some of these plants owe the success of their invasion, at least in part, to their beauty: dazzled by a well-turned branch, seduced by flowing racemes of colorful flowers, we've been duped into transporting them from foreign lands and giving them prominent positions in our backyards.
The following photos of invasive plants run the gamut from lowly weeds to towering trees. In between, you'll see examples of problematic vines and even a venerable landscape shrub, beloved in some quarters for serving as living privacy screens. Other shrubs qualifying as beautiful invasive plants are burning bush and butterfly bush.
01 of 16
Norway Maple Facts
Norway maple trees are widely admired for their fall foliage color. Many are drawn to another fact about them, as well: namely, the fact that they, like most of the oak trees, hold onto their foliage later into the autumn season than do many trees (thereby helping to extend the fall foliage season).
But when all the facts are in about Norway maple trees, a different picture will emerge for you as you try to decide whether to incorporate one into your landscaping as a specimen. Unfortunately, they are invasive plants in North America. Steve Nix, Forestry Expert, supplies a couple of other reasons why you might wish to reconsider planting Norway maples. Steve informs us of a bit of the history behind Norway maple's introduction to the U.S. in his comments on the trees' use in Central Park, New York, noting that they became substitutes for American elm trees after the Dutch elm disease debacle.
More Norway Maple Facts:
- Botanical name: Acer platanoides
- Zones: 3-7
- Height at maturity: 50-60 feet
- Variations in fall foliage color: Crimson King is grown for its dark leaves and does not offer the yellow fall foliage color seen in the photo above.
Watch the video on the About.com Trees and Shrubs website to learn some facts about telling Norway maples apart from other types of . Truly one of our fall foliage champions, maple trees are well worth including in your landscaping. It is easy enough to find one that is not invasive in North America. Examples that come to mind are Japanese maple trees and Autumn Blaze.
02 of 16
Silk Trees - Beautiful Invasive Plants
Invasive plants, mimosa (Albizia julibrissin) or "silk" trees are, nonetheless, unquestionably elegant and fast-growing. This low branching specimen with a spreading habit bears flowers with silky hairs, giving the tree its name. The fern-like leaves are an exquisite bonus. This delicate specimen gives a yard a tropical feel. Mimosa could easily serve as the poster child for this entire article: the beautiful invasive plant, par excellence.
Appropriately, silk trees hail from China, the destination of the Silk Road of ancient times. Silk trees will naturalize in warm areas, where they can become a nuisance. I occasionally see them here in New England, where winters are probably too cold for them to spread out of control. But in the South, their seedlings sprout up all over lawns, rendering them too high-maintenance, lovely or not.
Steve Nix offers another objection to growing silk trees: they do not live for very long (only 10 to 20 years).
03 of 16
Water Reed Plants: Useful Menace?
Why the oxymoron in my title? Well, water reed plants have traditionally been useful. In their native lands, they have been utilized in all sorts of ways. One of the more famous uses to which they have been put is as thatching for thatched roofs.
But if you are aware of the concept of "invasive plants," the story of the common reed (Phragmites) will be an all-too-familiar story by now. Brought to North America, water reed plants began exhibiting invasive tendencies, choking out natives in wetland environments. By the time folks realized there was a problem, they had spread out of control.
Many people find water reeds attractive, nonetheless; as my photo shows, they can be especially pretty in winter. They reach a height of over 6 feet (height will depend on the climate of the region where they are growing). Some people know water reed plants as "plumes," a common name bestowed upon them because of the feathery tufts that sit atop their tall stems.
04 of 16
Creeping Jenny Groundcover
Creeping jenny groundcover (Lysimachia nummularia) will tolerate shade. And this yellow-flowered creeper not only tolerates moist soil, but actually prefers it (I have found the plant growing along river banks while kayaking). These qualities, along with its yellow flowers, might make it seem to be an optimal choice for a groundcover. Unfortunately, though, nice-looking or not, this vine is an invasive plant. That's too bad, as flowering groundcovers are highly valued in landscaping.
Golden creeping jenny (Lysimachia nummularia 'Aurea') is even more tempting to grow. Grow it in a sunny location to maximize the golden color of its leaves. Some report that 'Aurea' is less aggressive than common creeping jenny.
Does creeping jenny sound too good to pass up? Are you conflicted over using it as a groundcover, since in that role it is a bit too successful (i.e., it spreads well and fills in an area: the function that a groundcover is supposed to perform)? Try growing creeping jenny in a container (as in my photo) so as to restrain it.
Incidentally, another common name for this plant, in lieu of "creeping jenny," is "moneywort." This latter common name, along with the specific epithet, nummularia (Latin for "coin-like"), refers to the shape of the leaves. The numerous, small, rounded leaves resemble a pile of coins, supposedly. Hey, don't blame me for these derivations; apparently, Linnaeus (and botanists who have followed in his footsteps) had a very good imagination!Continue to 5 of 16 below.
05 of 16
Purple Ajuga Choices and Other Types with Dark Leaves
I need to sound a warning about bugleweed (Ajuga), so named for the shape of the blue flowers that line its flower stalks: do not be lulled into a false sense of security by the sweet music it plays in the landscape! Like creeping jenny, it is a visually appealing groundcover (especially those with purple coloration), as my picture shows; unhappily, though, this groundcover is another invasive plant.
Beautiful in flower, the types with dark leaves (such as Ajuga 'Chocolate Chip') are still appealing even when not in bloom. Such foliage plants are the wise choice of gardeners in the know, as they offer a visual appeal more long-lasting than that found in plants whose main selling point is their colorful flowers.
Some cultivars have "purple" right in their names, letting you know they have purple leaves:
- Ajuga reptans 'Purple Brocade'
- Ajuga pyramidalis 'Purple Crispa'
Because Ajuga is an invasive plant, if you must grow it, grow it in areas where you want it to take over, not in flower beds. Grown in the latter, off-shoots from the original planting will have to be removed -- constantly! For example, Ajuga would work as an alternative to lawns, because it forms a mat and is tough enough to stand up to foot traffic.
06 of 16
Vinca Minor Groundcover: Option for Shade
Its pretty blue flowers and shade tolerance may make it attractive, but be aware that Vinca minor is considered an invasive plant.
Incidentally, Vinca major ("bigleaf periwinkle" or "big periwinkle") has bigger flowers but is less tolerant of shade and not as cold-hardy. Vinca major 'Variegata' is the most popular cultivar. This is a variegated foliage plant you often see cascading down the edges of hanging pots or window boxes. Because it is not as cold-hardy, I do not believe it is as invasive in the North as is Vinca minor.
07 of 16
Picture of St. John's Wort, Invasive Plant with Medicinal Properties
St. John's wort (Hypericum perforatum) is an invasive plant with medicinal properties. In fact, "touch-and-heal" is one of its other common names. Cathy Wong, About.com Guide to Alternative Medicine, calls it "one of the most commonly used herbs in the United States." As Cathy alludes to, the common name derives from the fact that, in its native Europe, the plant was observed to have bloomed at about the time of the birthday of St. John the Baptist.
This saint's birthday (June 24) falls right around Midsummer's Eve. That was a very special occasion in pagan times, marked, for example, by bonfires, upon which highly prized herbs would have been tossed, according to Richard Mabey. In his book, Weeds, Mabey writes (p. 75), "During the Middle Ages, the Midsummer fires were appropriated by the Christian Church, and said to be lit in honor of St John.... And the distinction of receiving the saint's name fell on the most magical of all the plants in the fire-mix," namely, St John's wort.
Also spelled "St. Johnswort," this invasive plant (invasive in North America, that is) is used to treat depression. It has naturalized in parts of the U.S. Some people find its bright yellow flowers pretty.
Do not confuse the perennial flower discussed above with the types of St. John's wort that come in shrub form and are grown for their colorful berries. These types belong to the same genus, Hypericum but are a different species.
08 of 16
Dame's Rocket: Mustard Family Femme Fatale
Dame's rocket (Hesperis matronalis) is indigenous to Eurasia and invasive in North America. Its colorful flowers make me wish that it were a native wildflower where I live; if it were, my perennial garden would not be without it. Indeed, I've witnessed beautiful displays of it in people's perennial gardens in the picturesque village of Stonington, Maine. While the plant is considered a short-lived perennial or even a biennial, it readily reseeds.
A member of the Mustard family, the "family ties" of dame's rocket provides a clue as to the degree of its invasiveness. Mustard family plants are notoriously aggressive. For example, garlic mustard (Alliaria petiolata) is one of the worst invasive plants in North America and lacks the beauty that partially redeems dame's rocket.
Indeed, no lovelier invader has ever stormed city walls. A mass of dame's rocket flowers such as the one shown in the picture here is truly hard to miss! To achieve the same Good 'N' Plenty look without invasive plants, grow white and pink garden phlox, instead.Continue to 9 of 16 below.
09 of 16
Butter and Eggs Plant or Toadflax: Not All Toads Are Ugly
The scientific name of butter and eggs plant is Linaria vulgaris. It also goes by the common names of "yellow toadflax" and "wild snapdragon." Anyone who has grown snapdragons in the garden can see the resemblance.
If you have been following along from Page 1 of this article, you know the drill by now: indigenous to Eurasia, butter and eggs plant was introduced into North America, where it has naturalized in many areas. A tough customer, this perennial tolerates poor soils.
"Butter and eggs" plant may be an innocent-sounding name (well, perhaps not if you are watching your cholesterol!), and the flowers are pretty, albeit small; but this delicate-looking beauty is considered an invasive plant. Like some of the other invasives considered here, it has been used medicinally in the past, including as a laxative.
The saying about having to kiss a lot of toads before finding a handsome prince implies that all toads are ugly. But the only thing ugly about yellow toadflax is its invasive quality.
10 of 16
Evening Primrose: Don't Be Led down This Primrose Path
While it has a nice yellow flower, as shown in the picture here, common evening primrose (Oenothera biennis) can be an invasive plant. As you can tell from the specific epithet, the plant is a biennial, the leaves forming a basal rosette the first year, then flowering and producing seed the second year. It takes that task of seeding very seriously, producing seed in copious amounts -- meaning lots of weed pulling if this is not a plant you wish to have growing all over your landscaping.
Nor is evening primrose an easy weed to pull out of the ground: the stems tend to break off, leaving the roots intact (from which evening primrose will continue to grow).
On the plus side, evening primrose has had some medicinal uses, traditionally. Amy Jeanroy, About.com Herb Gardens Guide, notes its usage for "treatment of PMS and menstrual complaints," for example.
Other types of evening primrose function as garden plants; for example, Missouri evening primrose (Oenothera macrocarpa), or "Ozark Sundrop."
11 of 16
Purple Loosestrife Flowers
Purple loosestrife flowers are hard to miss. Here we have another example of an invasive plant that, although a weed, could easily escape persecution due to its alluring good looks. Have you ever driven past a marsh and remarked upon the masses of pretty purplish blossoms growing in it? Chances are what you saw was this handsome invasive plant, which goes by the scientific name of Lythrum salicaria.
As you can see from my picture, purple loosestrife flowers are real lookers: growing en masse, these marsh plants form a veritable sea of color. So it is not surprising that the general public's response upon seeing purple loosestrife flowers tends to be positive, which infuriates conservationists to no end.
Indigenous to Eurasia, purple loosestrife flowers have taken over many marshes in the northeastern and northwestern regions of the U.S., choking out native vegetation.
Incidentally, plants in the Lysimachia genus are also frequently referred to as "loosestrifes." One example is gooseneck loosestrife (Lysimachia clethroides), a terribly invasive plant in its own right. While not commonly referred to as a loosestrife, another Lysimachia that is an invasive plant, Lysimachia nummularia, is described on Page 5. I have not found variegated yellow loosestrife (Lysimachia punctata 'Alexander') to be invasive here in New England.
12 of 16
Common Ivy: Invasive Groundcover
"Common ivy" and "English ivy" are common names for Hedera helix. A popular groundcover due to its attractive leaves, this groundcover is, nonetheless, considered an invasive plant in parts of North America.
An important word in that last sentence is "parts." The Pacific Northwest is known to be one part of the country where common ivy is an invasive plant. But unlike Japanese knotweed or purple loosestrife (the prior entry), it may not be invasive everywhere. Consult local experts if you are unsure of the plant's status in your own region.
Besides spreading out of control on the ground, common ivy also climbs trees, as my picture shows. Although its popularity even landed it a place in the Christmas carol, "The Holly and the Ivy," it's best to avoid planting this over-zealous vine. Many homeowners, having discovered what an uncommonly difficult task it is to eradicate common ivy, hate this groundcover as much as they would any weed.Continue to 13 of 16 below.
13 of 16
Trumpet Creeper: a Hummingbird Magnet, but at What Cost?
Trumpet creeper (Campsis radicans) is a good-news-bad-news story:
Granted, this unruly vine produces beautiful flowers. I know a number of people in my region (New England) were lured into planting trumpet creeper by promises that it would be a hummingbird magnet (which it is), only to learn later what an invasive plant it is.
A little tip here. If you wish to avoid potentially aggressive plants when you are shopping at the nursery, a red flag should go up when you see any of the following specific epithets on the plant label:
- radicans, as in Campsis radicans, trumpet creeper
- repens, as in Trifolium repens, white clover
- reptans, as in Ajuga reptans, bugleweed (see Page 6)
Both repens and reptans mean "creeping" in Latin, while radicans means "taking root." Each of those attributes helps make for a successful groundcover. Each of them also should raise healthy suspicions that the plant in question may have the potential to be an invasive plant. These species names often indicate that the plant in question spreads vigorously via underground runners.
14 of 16
Privet's Black Berries - What Evil Lurks Therein?
Privet isn't quite as attractive as some of the other invasive plants featured in these pictures, despite its dark blue berries in fall (so dark that they are practically black berries), as shown in this picture.
True, privet does also produce white flowers, and its fall foliage is a respectably attractive reddish-purple. But the popularity of privets is due largely to the dense foliage barrier they can provide when planted in a line and pruned into a hedge, a practice made famous by the British. There is a reason that "privacy" (as in "privacy fence") and "privet" sound a lot alike.
15 of 16
Oriental Bittersweet: Bitter Enemy of Trees
It would be tempting (although inaccurate) to think that the name of this vine originated from the dual nature of Oriental bittersweet, as in a "bittersweet victory". That is, the plant is one of North America's worst invasive plants, yet undeniably a sweet sight in the autumn.
The bittersweet picture here shows what the plant's immature berry look like in summer, before its husk dries to a rich gold color, from which orange berries erupt. The foliage in fall is also golden.
While the average land owner may have trouble relating to all the talk of invasive plants crowding out native species, there is nothing abstract about the problem posed by Oriental bittersweet. For all its beauty, this bittersweet is a menace to trees, constricting around their trunks tighter than any python could and eventually damaging them through girdling.
16 of 16
Bird's-Foot Trefoil: Wild Groundcover
Bird's-foot trefoil, or "birdsfoot trefoil" (Lotus corniculatus) is a creeper. This Old World native can be an invasive plant in North America, where it has f over a considerable range. A yellow wildflower (take careful note that "wildflower" is not synonymous with "native plant"), it serves as a wild groundcover.